1. Field of the Invention
The present invention generally relates to plasma processing of semiconductor wafers in the manufacture of integrated circuits (ICs) and, more particularly, to an apparatus for producing an inductive plasma for plasma processes, the apparatus having an improved radio frequency (RF) layered coil structure for inductively coupled plasmas (ICPs) which permits a certain amount of capacitive coupling to the plasma.
2. Background Description
Plasma processing is an indispensable technology in the manufacture of very large scale integrated (VLSI) circuits. Plasma-assisted etching techniques have replaced chemical etching, and sputtering has replaced evaporation for the deposition of metals. Plasma enhanced chemical vapor deposition (PECVD) is an alternative to conventional low pressure CVD techniques.
In some plasma processing applications of inductive plasmas, a nearly pure inductive plasma is desired, while in others, more capacitive coupling is desired. In presently used coils, there is a theta variation to the induced plasma current near the outer end of the RF coil. In most applications, the most efficient RF coil is desired. This is particularly true if some confinement of the plasma is being used near the RF coil which reduces the magnetic coupling coefficient of the RF coil.
The current design of inductively driven plasma sources does not address the issue of capacitive coupling to the plasma. This leads to nonuniformities in processing when dealing with polymerizing chemistries, and chemistries that have high activation energies.